Troubleshooting Engine Stalling in JLG 600AJN Aerial Lift

[MikePhua]

Introduction
The JLG 600AJN is a versatile aerial lift equipped with a Ford 425 carbureted engine, commonly used in various construction and maintenance tasks. However, some operators have reported issues with the engine stalling after warming up, particularly when engaging the dead man pedal. Understanding the potential causes and solutions for this problem is essential for maintaining the lift's performance and ensuring safety.
Common Causes of Engine Stalling

1. Fuel Delivery Issues
   

Fuel delivery problems are a primary cause of engine stalling. Potential issues include:

• Clogged Fuel Lines: Debris or sediment can obstruct fuel lines, restricting fuel flow.
  
• Faulty Fuel Pump: A malfunctioning fuel pump may not provide adequate fuel pressure.
  
• Vapor Lock: Excessive heat can cause fuel to vaporize in the lines, leading to vapor lock.
  

1. Ignition System Problems
   

An unreliable ignition system can cause the engine to stall:

• Worn Spark Plugs: Old or dirty spark plugs may not ignite the fuel-air mixture effectively.
  
• Faulty Ignition Coil: A malfunctioning coil can lead to weak or no spark.
  

1. Carburetor Issues
   

The carburetor plays a crucial role in mixing air and fuel:

• Dirty Carburetor Jets: Clogged jets can disrupt the air-fuel mixture.
  
• Incorrect Fuel Mixture: Improper adjustment can lead to stalling.
  

1. Electrical System Faults
   

Electrical issues can interrupt engine operation:

• Loose Wiring: Poor connections can cause intermittent power loss.
  
• Faulty Sensors: Malfunctioning sensors may send incorrect signals to the engine control unit.
  

Troubleshooting Steps

1. Inspect Fuel System
   

• Check Fuel Lines: Ensure there are no blockages or leaks.
  
• Test Fuel Pump: Verify it provides adequate pressure.
  
• Examine Fuel Filter: Replace if clogged.
  

1. Examine Ignition Components
   

• Inspect Spark Plugs: Clean or replace as necessary.
  
• Test Ignition Coil: Use a multimeter to check for proper resistance.
  

1. Clean Carburetor
   

• Disassemble Carburetor: Remove and clean all components.
  
• Check Jets: Ensure they are not clogged.
  

1. Check Electrical Connections
   

• Inspect Wiring: Look for loose or corroded connections.
  
• Test Sensors: Use diagnostic tools to verify sensor functionality.
  

Preventive Maintenance Tips

• Regularly Replace Fuel Filter: To prevent clogging.
  
• Use High-Quality Fuel: Reduces the risk of contaminants.
  
• Perform Routine Inspections: Check ignition and electrical systems periodically.
  

Conclusion
Engine stalling in the JLG 600AJN can result from various issues, including fuel delivery problems, ignition system faults, carburetor issues, and electrical system failures. By systematically troubleshooting these areas and performing regular maintenance, operators can ensure the lift operates efficiently and safely. Always consult the manufacturer's service manual for specific guidelines and procedures.